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Synthesis and Characterization of Polyimide Copolymers Containing Ladder-Like Polysiloxane

Feng, Linqian
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1406819476

Abstract Details

2014, PhD, University of Cincinnati, Engineering and Applied Science: Materials Science.
This research is focused on the synthesis, development, analysis and evaluation of properties of polyurea-b-polyimide (PUI) copolymers containing ladder-like polysiloxane. PUI block copolymers were successfully synthesized by condensation polymerization methods. The structure and properties of the copolymers were controlled by controlling the (i) co-monomer concentration and (ii) curing temperature. Thermally controlled self-assembly of semi-crystalline copolymers occurred at higher annealing temperatures T = 150°C, resulting in remarkable enhancement in their thermomechanical properties. The observed improvement in the structure and mechanical properties of the copolymers annealed at higher temperature is believed to be due to the development of inter and intra-hydrogen bonding interactions between adjacent copolymer chains. The dynamic mechanical property of the copolymers was determined by dynamic mechanical analysis (DMA) using solution cast thin films. Fourier transform infrared spectroscopy, FTIR and Wide angle X-ray diffraction (WAXD) method were used to study the composition and structure of the copolymers. The presence of hydrogen-bonded (H-bonded) polyimide units in the copolymer resulted in a significant enhancement in the corrosion protection of aluminum alloy 2024-T3. The corrosion performance of PUI coatings was studied by direct current polarization method (DCP) and electrochemical impedance spectroscopy (EIS) in a 3.5wt% NaCl solution. Corrosion performance was remarkably increased by increasing (i) polyurea concentration and (ii) annealing temperature. The coating lifetime was evaluated by using information from time-based Bode plot as well as gravimetric weight gain analysis. The surface energy and diffusivity of PUI copolymers were remarkably decreased as polyurea concentration increased. Semi-crystalline ladder-like polysiloxanes (LPS) containing both mercapto and fluoride side groups were synthesized by using both the sol–gel and monomer self-assembly methods. Subsequently, LPS was incorporated into PUI copolymer followed by imidization. It was shown that full imidization can be achieved at a relatively low temperature of 150°C. It was also shown that the presence of LPS in the copolymer significantly decreased the surface energy, improved the damping ability and thermal dimensional stability of the thin films.
Jude Iroh, Ph.D. (Committee Chair)
Rodney Roseman, Ph.D. (Committee Member)
Vesselin Shanov, Ph.D. (Committee Member)
Donglu Shi, Ph.D. (Committee Member)
116 p.
Materials Science

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Citations

  • Feng, L. (2014). Synthesis and Characterization of Polyimide Copolymers Containing Ladder-Like Polysiloxane [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1406819476

    APA Style (7th edition)

  • Feng, Linqian. Synthesis and Characterization of Polyimide Copolymers Containing Ladder-Like Polysiloxane. 2014. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1406819476.

    MLA Style (8th edition)

  • Feng, Linqian. "Synthesis and Characterization of Polyimide Copolymers Containing Ladder-Like Polysiloxane." Doctoral dissertation, University of Cincinnati, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1406819476

    Chicago Manual of Style (17th edition)

ucin1406819476
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This open access ETD is published by University of Cincinnati and OhioLINK.